Printer

Abstract

A duplex printer with a small, compact conveyance path has a medium supply path and a medium inverting path that merge into a middle conveyance path at a junction. The middle conveyance path goes to a path switching unit connecting a main conveyance path and the inverting path. A flap, which is a path switching member, is disposed in the path switching unit. A middle conveyance roller pair, having a middle conveyance roller and a nipping portion, conveys the medium (e.g. paper) through the middle conveyance path. The portion of the middle conveyance path from at least the junction to the nipping portion is a conveyance path portion defined by the roller surface of the middle conveyance roller. The paper fed to the middle conveyance path is guided by the middle conveyance roller from the junction to the nipping portion of the middle conveyance roller pair.

What is claimed is: 
     
       1. A printer comprising:
 a media supply path that conveys a medium to be printed upon; 
 a first conveyance path that conveys the medium past a print position, the direction of conveying the medium to the printing position for printing being the downstream direction of the first conveyance path; 
 a looped inverting path that reverses the front and back sides of the medium; 
 a junction where the downstream end of the media supply path and the downstream end of the inverting path merge; 
 a second conveyance path extending from the junction to a path switching unit where the upstream end of the first conveyance path and the upstream end of the inverting path merge; and 
 a conveyance roller pair that conveys the medium from the junction toward the path switching unit, the conveyance roller pair having a drive roller and a nipping portion; 
 wherein the medium is guided by a conveyance roller from the junction to the media nipping portion of the conveyance roller pair, said conveyance roller being the drive roller of the conveyance roller pair; 
 
       wherein:
 the upstream end of the first conveyance path has a conveyance guide surface that faces the conveyance roller and guides media conveyed by the conveyance roller pair; 
 the conveyance roller has an outside roller surface that rotates away from the conveyance guide surface in the downstream direction of the first conveyance path; and 
 the path switching unit includes a path switching member having a first member surface on a side facing away from the conveyance roller and a second member surface opposite the first member surface on a side facing the conveyance roller, a first switching-member guide surface being formed on the first member surface and a second switching-member guide surface being formed on the second member surface; 
 the path switching member being movably switchable between a first switching position and a second switching position, wherein the first switching position guides media, that is conveyed from the first conveyance path to the path switching unit, to the inverting path, and the second switching position guides media, that is conveyed from the second conveyance path to the path switching unit, to the first conveyance path, said path switching member being biased toward said first switching position in a resting state and requiring a pushing force to be moved to said second switching position; 
 in said first switching position, the second switching-member guide surface being proximate to the conveyance roller and the distal end of the second switching-member guide surface, that is closest to the first conveyance path, facing the outside roller surface of the conveyance roller; 
 when medium is conveyed to the path switching unit by the conveyance roller pair, the medium pushes on the second switching-member guide surface and pushes the path switching member to said second switching position; and 
 in the second switching position, the second switching-member guide surface being moved away from the conveyance roller, and the distal end of the first switching-member guide surface, that is closest to the first conveyance path, being at a position moved away from the conveyance guide surface of the first conveyance path. 
 
     
     
       2. The printer described in  claim 1 , wherein:
 the conveyance roller and a media guide opposite the conveyance roller guide the medium along the media supply path to the junction from a position a specific distance upstream from the junction on the media supply path. 
 
     
     
       3. The printer described in  claim 2 , wherein:
 the media guide has a media pressure surface that presses the medium toward the conveyance roller. 
 
     
     
       4. The printer described in  claim 1 , wherein:
 the first distal end of the first switching-member guide surface, that is closest to the first conveyance path, being an upstream end-side first guide surface; 
 the second distal end of the first switching-member guide surface opposite the upstream end-side first guide surface being a downstream end-side first guide surface; 
 the portion of the first switching-member guide surface between the upstream end-side first guide surface and the downstream end-side first guide surface being a middle first guide surface; and 
 in the first switching position:
 the upstream end-side first guide surface is defined by a downward sloping plane that slopes from the middle first guide surface toward conveyance roller, 
 the downstream end-side first guide surface is defined by a substantially horizontal plane that extends in a feed direction of medium conveyed from the first conveyance path toward the inverting path, and 
 the middle first guide surface defined by a curve smoothly connecting the upstream end-side first guide surface to the downstream end-side first guide surface. 
 
 
     
     
       5. The printer described in  claim 1 , wherein media conveyed through the media nipping portion to the path switching unit contacts a flat part of the second switching-member guide surface. 
     
     
       6. The printer described in  claim 1 , wherein:
 the switching member includes a plurality of ribs extending in a first feed direction of medium conveyed from the first conveyance path toward the inverting path, the plurality of ribs being disposed at regular intervals widthwise relative to the first feed direction, the switching member further including connector parts connecting the ribs widthwise; and 
 a top edge of each rib being a respective one of said first member surface, and a bottom edge of each rib being a respective one of said second member surface. 
 
     
     
       7. The printer described in  claim 6 , wherein:
 the conveyance roller has a roller shaft, and a plurality of roller segments disposed with a specific gap therebetween on the roller shaft; and 
 the ribs are disposed widthwise relative to the conveyance path on both sides of the roller segments. 
 
     
     
       8. The printer described in  claim 1 , further comprising:
 a media separation mechanism that separates and conveys the media one sheet at a time through the media supply path; 
 the media separation mechanism including the conveyance roller, and a retard roller configured to contact the conveyance roller. 
 
     
     
       9. The printer described in  claim 1 , further comprising:
 a main conveyance roller pair that conveys the medium through the first conveyance path; 
 a power supply that rotationally drives the main conveyance roller pair; and 
 a power transfer mechanism that transfers drive power from the power supply to the conveyance roller to rotationally drive the conveyance roller in the direction conveying the medium to the path switching unit. 
 
     
     
       10. The printer described in  claim 1 , wherein path switching member is a flap freely pivotal about a pivot point. 
     
     
       11. The printer described in  claim 10 , wherein:
 said first switching position is the resting state of said flap; 
 said flap is biased toward said first switching position by gravity; and 
 said second switching position is a displacement position of said flap when pivoted against gravity about said pivot point.